Abstract: This paper deals with the conditions for criticality and other related problems for the continuous-flow stirred tank reactor(CSTR) operating adi-abatically under steady state. A new technique for analyzing the thermally sensitive region of adiabatic CSTR is discussed, and mathematical expressions for two important thermally sen sitive boundaries, ignition and extinction, are given. A new concept on the transition phenomenon or the dis appearance of criticality is pointed out theoretically, and expressions for the conditions of this transition to occur are given. The present paper finally discusses the times-to-ignition for marginally supercritical systems, which are very close to the thermally sensitive boundary of ignition.